


Sans didn’t know what he was getting into.

by Jennajen



Series: One-Shots [3]
Category: Undertale
Genre: F/M, Obsession, Obsessive Behavior, Possessive Behavior, Underfell Sans (Undertale), Yandere Sans (Undertale), how to tag, only a mention of papyrus
Language: English
Status: Completed
Published: 2018-12-20
Updated: 2018-12-20
Packaged: 2019-09-23 05:46:51
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,522
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17074517
Author URL: https://archiveofourown.org/users/Jennajen/pseuds/Jennajen
Summary: He really, really didn't. But he didn't really want to stop, either. It was like an addiction. A poisonous one that pulled him from his brother and his home - but he was the happiest he's been in the longest time. Like hell he was going to stop.





	Sans didn’t know what he was getting into.

**Author's Note:**

  * For [Sonamyluffer101](https://archiveofourown.org/users/Sonamyluffer101/gifts).



> I figured I might as well post this now before I keep writing and never find a stopping point - never posting it. This is for you, [Sonamyluffer101](https://archiveofourown.org/users/Sonamyluffer101/works) . Merry Christmas.

Sans didn’t know what he was getting into.

 

He just… he literally just met you, for fucks sake. Seriously, like, two fucking minutes ago. What the hell was wrong with him. You were kind to him, you weren’t racist. So fucking what? You bumped into him as you were walking home, apologized, and were on your way. That was  _ it _ .

 

…

 

So  _ why the fuck _ was he following you home?!

 

You didn’t know he was there, of course. He wasn’t that stupid. He made sure to stay out of your sight. If he didn’t stay away, then you might have ended up calling the police or some shit. 

 

…

 

…

 

He was just curious, that’s all. Just plain old curiosity and suspicion. Right. Yeah.

 

Of course.

 

No human would ever be so offhandedly nice to a monster.

 

That was all this feeling was. 

 

Suspicion.

 

He was suspicious of you, and that was why he watched you step through the door and into your own home. He was curious, and that was the only reason he took a quiet shortcut inside that same home and into a slightly open closet, watching you as you got comfortable on the couch to watch a show, after you had put your outdoor stuff down and away. The only reason that he watched you watch a show the rest of the night was because you were new, different. There was  _ no other reason _ .

 

But he knew he couldn’t fool himself for long. There was just… something about you. He couldn’t take his mind or eyes off of you. He needed to know more. He didn’t know you, and that just added to his curiosity. It was like love at first sight, but he knew that didn’t exist. That was just stupid.

 

“...Is anybody there?” You asked the seemingly empty room. Huh, it seemed like you had turned the tv off during his internal monologuing. That was bad, you could probably feel his eyes on you. You might have been a little freaked out, in all honesty.

 

He couldn’t blame you. He really was a creep.

 

He should have just gone home. What was the point of all this, anyway? He didn’t even know you.

 

…

 

Then again… he didn’t really want to go home, either. Home was horrible, where Boss was always up his ass about anything and everything, and he didn’t want to deal with that.

 

So… why not just stay here? With you? You didn’t know he was there, but that was okay. He could watch over you and keep you safe. He could also find out more about you, and see why he was suddenly so obsessed. Obsessed was the right word, right? He couldn’t think of anything else.

 

He watched as you slowly turned your show back on, having heard nothing in response to you call.

 

That was something he had to be careful of. He couldn’t be watching you to the point where you felt creeped out and thought correctly that somebody was in your house. He had to remain inconspicuous. He didn’t need you finding out about him and calling the police. He didn’t need you afraid.

 

* * *

 

Before he knew it, two years had passed. He hadn’t once returned back to his own home unless it was to grab some clothes and sleeping supplies from his room. Over the years, he had learned how to live practically beside you without you even having a suspicion that he was there. He made sure that you were always in his sight, except for when you were in the bathroom. He’d give you some privacy in the bathroom.

 

His brother had called or texted him from time to time, but he didn’t pay him much mind. It wasn’t like his brother even  _ cared _ , for fucks sake. Nevertheless, Sans let him know through text and verbal confirmation (out of hearing range of you, of course) that he was  _ perfectly fine. _ That didn’t seem to dissuade Boss from trying to contact him again and again, however.

 

He got to watch your live your life for a little over two years, and he only really did fall more in love. Yeah, he admitted it to himself somewhere around last year. He loved you. He loved you so much that he was obsessed and possessive. He wanted to know every single little detail about you, and he wanted to be with you. He wanted to marry you. He wanted to stay with you every single day for the rest of his life.

 

Before he met you, he was honestly huge on one night stands. He loved to be with as many people as possible. Loved to figure out what made them tick. He was also willing to admit that he was afraid. He was afraid of being in a serious relationship with anybody. But now… there was nothing he wanted more with you. He hadn’t even gone back to a bar or Grillby’s since he met you, and he honestly couldn’t say that he cared.

 

...Okay, well, that wasn’t true. He couldn’t just stay away from Grillby’s like that. Especially when Grillby was the only one who had his special mustard, and alcohol. He just stopped getting drunk (he feared showing himself to you because he wasn’t in his right mind), and he stopped accepting any one-night stand offers.

 

Some monsters were starting to give him weird looks. He wasn’t acting like himself.

 

But that was fine. All he really needed was you. He didn’t care about what anybody else thought of him, not even his own brother or Grillby.

 

The only person’s thoughts of him that he cared about was yours. He was scared you’d be afraid of him. Hate him, even.

 

...What was he supposed to do if you were scared of him or hated him?

 

He didn’t know. He didn’t want to know. He didn’t want that to happen. He was going to make sure it  _ didn’t _ happen, even if that meant never speaking to you or showing himself to you, ever.

 

The one thing he was thankful for, however, was the fact that you never seemed interested in dating. You hardly ever even left the house, and when you did, you never talked to anyone. You always stuck to yourself, and avoided as much confrontation as possible. If he had to guess, you probably had some sort of social anxiety or whatnot that prevented you from doing so. But he wasn’t going to guess, because he didn’t want to assume things about you.

 

…

 

But… as the days passed, turned to weeks, and eventually turned to months, he found himself feeling rather lonely. Even though he was around you all the time, he had been wanting more and more to show himself to you. What would happen, though, if he showed himself, and you hated him? Heh. He hated himself, why would you be any different? He’s a huge scary skeleton monster with sharp teeth and a golden fang, with his eyelights as red as blood. Plus, he has a huge obsession over you.

 

You’d hate him.

 

…

 

But he really wanted to talk to you. To interact with you. He didn’t want to hide in the shadows anymore. You’d hate him, though. He knew you would.

 

…

 

...Well, he  _ could _ start interacting with you without you knowing he watched you like he did.

 

Yeah, okay. And then you would be less likely to hate him. He could also bribe you with gifts and shit, too. And you weren’t  _ racist _ , so...

 

…

 

_ Fuck, why was he knocking on your door?! _

 

When you opened the front door, he was gone. And he immediately felt guilty. He just ding dong ditched you, what the hell was he thinking? He was being an asshole. And while he may have been an asshole on a regular basis, he swore he would never be an asshole to you. He wanted you to see the best of him.

 

He needed a better way to interact with you.

 

What if… he ‘bumped into you’ at the store? He was taller than you, maybe he could do the cliche thing where he grabbed something for you on a higher shelf? That might be a possibility.

 

Okay… okay, he was going to do that. Which was good, because today was the day that you went to the store. He watched as you got ready to go, staring shamelessly as you got naked, and then got dressed. 

 

Fuck, he loved you. He loved every inch of your body. He could tell you didn’t like your body, but he didn’t understand why, though, because you were literally perfect. You were perfect, the entirety of you.

 

...Back on topic. You were just barely getting there when he finally got out of his own head long enough to pay attention to you. He watched fondly as you grabbed a cart and pushed it into the store.

 

Alright… you were going to get milk first. That was great. It was time to finally meet you. He was so fucking excited.

 

...Oh, no, wait. The milk carton was easily accessible. Nevermind. Pasta aisle. Okay, maybe… Nope. Nevermind. You were getting oreos, but those were always on a lower shelf. Yep. He was right.

 

All too soon, you were already checking out and heading home. Dammit. What the fuck was he supposed to do now? Bump into you?

 

...Actually, that wasn’t such a bad idea. It was short and simple. And it was how he found out about you in the first place. Okay, he had to time this perfectly, but it should be pretty simple. All he had to do was wait until you weren’t looking where you were going, and…

 

_ Bump. _

 

You stepped back a little, and mumbled out a little apology before you stepped to the side to let him pass. Now that just wouldn’t do. You wouldn’t even look at him.

 

“...hey,” He all but whispered, reaching over to catch your arm so you would stop. You looked at him, and he began to sweat. “i, um… i’m sans. sans the skeleton. uh. nice to meet you?”

 

THIS WAS FUCKING AWKWARD.

 

How does one start a conversation??

 

Okay, okay, try again. It was not too late to try again.  _ Don’t blow it now. _ “umm... what’s your name?”  _ He already knew damnit. _

 

“...y/n.” You gave him a look, confused. “...Have I seen you somewhere before?”

 

He shrugged. “depends. have you seen a living skeleton around somewhere before?”

 

“...Yes?” You looked so confused, it was adorable. “I don’t… know. I don’t really talk to people.”  _ Good _ .

 

“well, fifty - fifty chance that it was me, if you have.”

 

“...Fifty - fifty?”

 

“mhm. i have a brother, and we’re the only skeletons.”

 

“Huh. So half and half?”

 

He nodded in agreement.

 

“Then I think I might’ve seen you before. What’s your brother like?” You looked like you were trying to decipher a code.  _ cute. _

 

“super tall, rude as shit, super spikey, and obsessed with lasagna.”

 

“...Spikey?”

  
“...out of everything i said,  _ that’s _ what got your attention?”

 

“Well, how in the world is somebody spikey?”

 

“shit, i don’t know. probably defies the laws of physics or something.”

 

You giggled, “How tall is he?”

 

“like, seven foot six or something equally as impossible. would you believe he’s the younger brother?”

 

You were getting comfortable around him. He could tell by your relaxing shoulders and back, and by how you looked at him as well. You actually looked at his face for longer than if you would if you weren’t comfortable around him. Your posture was different, and you were leaning more towards him than away from him, which was how you were standing at the beginning of the conversation.

 

“Okay, yeah, definitely defies the laws of physics.” And, god, your  _ smile _ . You were smiling  _ at him _ , and your smile was  _ genuine _ . He felt like he could die happy right then and there.

 

“heh. yeah.”

 

…

 

_ fuck. awkward silence. _

 

“Hey, uh… I have to get going.”

 

He masked the disappointment in his tone with something more steady. “oh. right, sorry.”

 

“...But…”

 

…?

 

“This… is going to sound weird, since we just met and all.”  _ oh trust me, sweetheart, nothing you say could sound weird. _ “...Can I have your number? I don’t really want to stop talking to you.”

 

He froze and blinked owlishly. You didn’t… you couldn’t have. Did you? Did you really just ask him what he thought you asked him?

 

“...Sorry. Nevermind. It was a stupid thing to ask. We just met.”

 

_ shit _ . You really did just ask him that, and he just stood there like an  _ idiot _ and let you believe what you asked was wrong. “no!” He rushed, “i mean - yes.”  _ fuck. _ “i mean, no, it’s not weird, yes, you can have my number. uh.” He fumbled for a second to pull is dirty, giant, old boxlike phone out of his pocket and hand it to you. “here.”

 

You seemed amused by his antics. Good. That meant you were feeling better about the situation. That was, sadly, until you looked down and caught sight of his phone. Then your expression turned from amused to what seemed to be a light version of horrified.

 

...What was wrong with his phone? Sure, it wasn’t a touch screen like yours was, but it still worked perfectly fine? Maybe it was because it was dirty? But he knew you weren’t that kind of person, so he wasn’t worried about you thinking it was too dirty. ...Or should he be?

 

“It’s… so  _ old _ .”

 

…

 

_ um. _

 

“...old?” He mirrored, choking back laughter.  _ That’s _ what’s got you so worked up?

 

“Yeah. Like…” you did some hand motions while holding his apparently old phone, “it’s not even a flip phone, it’s that old.”

 

He chuckled, “aren’t flip phones those small cute phones?”

 

“Yes. And they’re old.” You seemed to stand very firm in your statement.

 

Sans managed to keep his face straight, even though his soul was practically melting with his love for you - his obsession over you - and how you were acting at the moment. You were acting adorable, and sweet, and kind, and -  _ he just wanted to fucking love on you _ . Hug you, smother you with kisses, pin you down and fuck you until you’re crying and begging for m-

 

...Yeah, don’t go down that road of thought. At least not right now, with you standing right in front of him.

 

* * *

 

...Overall, the whole exchange turned out pretty good in the end. Hopefully, at least, considering he was still in fact standing on the sidewalk where you left him, staring at his contact list that contained your name with what he hoped weren’t heart-shaped eyelights. He’d seen himself in the mirror when he’d been feeling the same as he was at the moment, and he saw burning red heart eyes staring right back at him, fueled by his love obsession with you.

 

But he shook himself out of his fantasy that was going to not so appropriate places. Now was not the time for that. Now was the time to stalk you - again.

 

He still didn’t know what he was doing, but he fucking loved it.

**Author's Note:**

> [My Tumblr](http://multimod.tumblr.com/)  
> [My Pillowfort](https://www.pillowfort.io/JennaJen/) , where I'll be mostly posting now.
> 
> Now, back to writing my main fic.


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